The invention concerns a ram device with a cylindrical housing in which is arranged a pressure medium actuated impact piston and a control unit for controlling the pressure medium flow into the housing and which housing at a rearward end is provided with a pressure medium connector and is closable by a closure part which closure part is threadable into an end section of the housing provided with an internal thread by a first externally threaded section of the closure part.
Among ram devices of the above-mentioned kind, are understood to be ram boring devices, especially pressurized air driven earth rockets, steel tube rams or pipe splitting machines. In the assembly of such ram devices, as is known, for example, from DE 196 37 697 A1, the housing is customarily connected with a workhead, for example a boring head or splitting head, with the particular kind of connection not being of closer interest here. After the insertion of the impact piston into the housing, a control unit and closure part, which are also referred to as a threaded end module, are preassembled and then together threaded into the housing.
It is known to adhesively bond the externally threaded section of the closure part to the internally threaded portion of the housing to inhibit unwanted loosening of the closure part during impacting operation. For this, a metal adhesive is used. In order for this adhesive to provide a reliable bond, the housing at its rear threaded portion must be heated after the assembly for a period of 10-20 minutes depending on the diameter of the device. This heating is accomplished by means of an electrical heating cuff. For disassembly, the device must be heated for as long as 20-60 minutes to again relax the metal adhesive.
An earth rocket is known from U.S. Pat. No. 5,487,430 in which the closure part is threaded into the housing until it comes into abutting engagement with the housing. Subsequently, an end cone is attached to the rearward end of the housing and is secured by threaded bolts which are received in threaded bores formed in the closure part. This solution makes it difficult to ensure that the control unit connected with the closure part stands in a given rotary position with respect to the impact piston as can be necessary for the control of the forward and rearward running of the ram device.
Further, with this solution, the disassembly of the closure part is bothersome because of the many bolts. The bolts during operation become bound up very tightly so that a disassembly at the construction site is often not possible and the device has to be transported to the workshop.
Further, a ram boring device with a cylindrical housing is known from DE 42 21 471 A1 in the rearward end of which an intermediate piece is threaded and into which in turn is threaded an end piece, in order to fix to the end piece a support ring for a pusher, with the support ring having an air discharge bore.
The invention has as its basic object, to so construct a ram device of the initially mentioned kind that the closure part can be reliably secured in its assembled position by simple means and can thereafter be again removed in a few minutes without the ram device for this procedure having to be transported to a workshop.
This object is solved in accordance with the invention in that the closure part has a second threaded section which stands in threaded engagement with a counter element, which counter element abuts a housing surface normal to the housing axis.
Preferably the second threaded section is likewise formed by an external thread on the outer circumference of the closure part.
The solution of the invention enables the securing of the closure part in such desired rotary position relative to the housing that the control unit also can take a desired position relative to the housing and to the impact piston. When the ram device must be unscrewed for maintenance or repair procedures, this can take place at the construction site. It is not necessary that the ram device for this be transported into a workshop.
Preferably the pitch of the winding of the first threaded section is at least twice as large as the pitch of the thread of the second threaded section. Therefore, the first thread can be a coarse trapezoidal thread and the second thread can be a fine thread, with the pitch of the trapezoidal thread, for example, being three times as large as that of the fine thread.
In an especially simple embodiment, the counter element is a counter ring provided with an internal thread. In this case, the second externally threaded section of the closure part is preferably chosen to be so long that an end cone closing the housing is threadable onto this second externally threaded section of the closure part.
In a further embodiment of the invention, the counter ring has a rearward externally threaded section onto which in turn the end cone is threadable. Here again, the thread of the externally threaded section of the counter ring is preferably a fine thread.
In the case of a ram device whose housing at its rear end has an externally threaded section onto which the closure part provided with an internally threaded section is threadable, the further threaded section can likewise be formed as an internally threaded section, into which the counter ring provided with an external thread can be threaded.